This weekend's Wall Street Journal had a piece on home field advantage in sports, and cited statistics which evidenced the impact of home crowds, as well as what different sports are doing to enhance their advantage. College basketball stadiums moving their student crowds closer to the court exemplified these efforts.
According to statistician Jeff Sagarin, "if two teams of equal ability play, the home team would be expected to win 61% of the time in the NFL, over 65% of the time in the NBA, and almost 70% of the times in college basketball." Contributing elements to the home-field advantage also include familiarity with the court and conditions, as well as lack of enduring the impact of traveling to the game.
In baseball, the teams with the biggest differential between their home and away winning percentages (over the last ten years) were the Colorado Rockies, Florida Marlins, Washington Nationals/Montreal Expos, Texas Rangers, and Tampa Bay Devil Rays. All five of these teams are pretty bad overall (save the Marlins' 1997 and 2003 championship years).
Does this mean that the home-field advantage isn't relevant enough in baseball to impact a good team? That good teams just play through it, irrespective of what stadium in which they're playing?